Tool bit

ABSTRACT

A method of manufacturing a tool bit includes machining a working end into a piece of hexagonal bar stock. A shank adjacent the working end is machined, leaving a hexagonal drive portion adjacent the shank. The tool bit is heat treated, and a coating is applied to the working end, the shank, and the hexagonal drive portion of the tool bit to inhibit corrosion of the tool bit. At least a portion of the shank is polished to remove the coating from the portion of the shank.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent application Ser. No. 12/669,200 filed Jan. 15, 2010, which is a national phase application under 35 U.S.C. §371 of International Patent Application No. PCT/US2009/063515 filed Nov. 6, 2009, which claims priority to U.S. Provisional Patent Application No. 61/112,318 filed Nov. 7, 2008, the contents of all of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to tool bits, and more particularly to tool bits configured for interchangeable use with a driver.

BACKGROUND OF THE INVENTION

Tool bits, or insert bits, are often used with drivers configured to interchangeably receive the bits. For example, typical insert bits each include a hexagonal drive portion, a head or tip configured to engage a fastener, and a cylindrical shank connecting the drive portion and the tip. Drivers include a socket having a hexagonal recess in which the hexagonal drive portion of an insert bit is received and a stem or shank extending from the socket, which can be coupled to a handle for hand-use by an operator, or a power tool (e.g., a drill) for powered use by the operator. An interference fit between the hexagonal drive portion of the insert bit and the socket may be used to axially secure the insert bit to the driver, or quick-release structure may be employed to axially secure the insert bit to the driver.

SUMMARY OF THE INVENTION

The invention provides, in one aspect, a method of manufacturing a tool bit. A working end is machined into a piece of hexagonal bar stock. A shank adjacent the working end is machined, leaving a hexagonal drive portion adjacent the shank. The tool bit is heat treated, and a coating is applied to the working end, the shank, and the hexagonal drive portion of the tool bit to inhibit corrosion of the tool bit. At least a portion of the shank is polished to remove the coating from the portion of the shank.

Other features and aspects of the invention will become apparent by consideration of the following detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a tool bit according to one construction of the invention.

FIG. 2 is a side view of the tool bit of FIG. 1.

FIG. 3 is a top view of the tool bit of FIG. 1.

FIG. 4 is a front view of the tool bit of FIG. 1.

FIG. 5 is a rear view of the tool bit of FIG. 1.

FIG. 6 is exploded perspective view of the tool bit of FIG. 1.

FIG. 7 is a perspective view of a tool bit according to another construction of the invention.

FIG. 8 is a side view of the tool bit of FIG. 7.

FIG. 9 is a top view of the tool bit of FIG. 7.

FIG. 10 is a front view of the tool bit of FIG. 7.

FIG. 11 is a rear view of the tool bit of FIG. 7.

FIG. 12 is a perspective view of a tool bit according to another construction of the invention.

FIG. 13 is a side view of the tool bit of FIG. 12.

FIG. 14 is a top view of the tool bit of FIG. 12.

FIG. 15 is a front view of the tool bit of FIG. 12.

FIG. 16 is a rear view of the tool bit of FIG. 12.

FIG. 17 is exploded perspective view of a tool bit according to yet another construction of the invention.

FIG. 18 is an assembled side view of the tool bit of FIG. 17.

FIG. 19 is a perspective view of a tool bit according to one construction of the invention.

FIG. 20 is a side view of the tool bit of FIG. 19.

FIG. 21 is a front view of the tool bit of FIG. 19.

FIG. 22 is a rear view of the tool bit of FIG. 19.

FIG. 23 is a perspective view of a tool bit according to another construction of the invention.

FIG. 24 is a side view of the tool bit of FIG. 23.

FIG. 25 is a front view of the tool bit of FIG. 23.

FIG. 26 is a rear view of the tool bit of FIG. 23.

FIG. 27 is a perspective view of a tool bit according to another construction of the invention.

FIG. 28 is a side view of the tool bit of FIG. 27.

FIG. 29 is a front view of the tool bit of FIG. 27.

FIG. 30 is a rear view of the tool bit of FIG. 27.

FIG. 31 is a perspective view of a tool bit according to yet another construction of the invention.

FIG. 32 is a side view of the tool bit of FIG. 31.

FIG. 33 is a front view of the tool bit of FIG. 31.

FIG. 34 is a rear view of the tool bit of FIG. 31.

FIG. 35 is a perspective view of a tool bit according to yet another construction of the invention.

FIG. 36 is a side view of the tool bit of FIG. 35.

FIG. 37 is a front view of the tool bit of FIG. 35.

FIG. 38 is a rear view of the tool bit of FIG. 35.

FIG. 39 is a perspective view of a tool bit according to one construction of the invention.

FIG. 40 is a side view of the tool bit of FIG. 39.

FIG. 41 is a front view of the tool bit of FIG. 39.

FIG. 42 is a rear view of the tool bit of FIG. 39.

FIG. 43 is a perspective view of a tool bit according to another construction of the invention.

FIG. 44 is a side view of the tool bit of FIG. 43.

FIG. 45 is a front view of the tool bit of FIG. 43.

FIG. 46 is a rear view of the tool bit of FIG. 43.

FIG. 47 is a perspective view of a tool bit according to another construction of the invention.

FIG. 48 is a side view of the tool bit of FIG. 47.

FIG. 49 is a front view of the tool bit of FIG. 47.

FIG. 50 is a rear view of the tool bit of FIG. 47.

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

DETAILED DESCRIPTION

FIGS. 1-6 illustrate a tool bit or an insert bit 10 including a hexagonal drive portion 14, a head or tip 18 configured to engage a fastener, and a shank 22 interconnecting the drive portion 14 and the tip 18. The hexagonal drive portion 14 is intended to be engaged by any of a number of different tools, adapters, or components to receive torque from the tool, adapter, or component to rotate the insert bit 10. For example, the insert bit 10 may be utilized with a driver including a socket (not shown) having a corresponding hexagonal recess in which the hexagonal drive portion 14 of the insert bit 10 is received. The driver may also include a stem extending from the socket, which may be coupled to a handle for hand-use by an operator or to a chuck of a power tool (e.g., a drill) for powered use by the operator. An interference fit between the hexagonal drive portion 14 of the insert bit 10 and the socket may be used to axially secure the insert bit 10 to the driver. Alternatively, a quick-release structure may be employed to axially secure the insert bit 10 to the driver. With reference to FIGS. 1-3, the drive portion 14 of the insert bit 10 includes a groove 26 into which the quick-release structure (e.g., a ball detent) may be positioned to axially secure the insert bit 10 to the driver. Alternatively, the groove 26 may be omitted from the drive portion 14 of the insert bit 10 should an interference fit between the socket and the drive portion 14 be employed.

With continued reference to FIGS. 1-3, the tip 18 of the insert bit 10 is configured as a Philips-style tip 18 (see also FIG. 4). Alternatively, the tip 18 of the insert bit 10 may be differently configured to engage different style fasteners. For example, the tip 18 of the insert bit 10 may be configured as a straight blade (otherwise known as a “regular head”) to engage fasteners having a corresponding straight slot. Other tip configurations (e.g., hexagonal, star, square, etc.) may also be employed with the insert bit 10.

With reference to FIGS. 1-3, a portion 30 of the shank 22 is concave, including opposite end portions 34 and a reduced diameter mid-portion 38. Specifically, the concave portion 30 of the shank 22 includes an outer peripheral surface 42 having a curvature in a plane including a central axis 46 of the insert bit 10 (i.e., in a plane parallel to the plane of the page of FIGS. 2 and 3). In a configuration of the insert bit 10 having an overall length Lt of about 1 inch, the curvature is defined by a radius R of about 0.15 inches to about 0.75 inches. Alternatively, in a configuration of the insert bit 10 having an overall length Lt of about 2 inches, the curvature is defined by a radius R of about 0.85 inches to about 2.75 inches. Further, in a configuration of the insert bit 10 having an overall length Lt of about 3 inches, the curvature is defined by a radius R of about 7 inches to about 15 inches.

With continued reference to FIGS. 1-3, in a configuration of the insert bit 10 having an overall length Lt of about 1 inch, the length L of the concave portion 30 of the shank 22 is about 0.2 inches to about 0.35 inches (i.e., the ratio of L/Lt is about 0.2:1 to about 0.35:1). Alternatively, in a configuration of the insert bit 10 having an overall length Lt of about 2 inches, the length L of the concave portion 30 of the shank 22 is about 0.5 inches to about 0.7 inches (i.e., the ratio of L/Lt is about 0.25:1 to about 0.35:1). Further, in a configuration of the insert bit 10 having an overall length Lt of about 3 inches, the length L of the concave portion 30 of the shank 22 is about 1.5 inches to about 1.8 inches (i.e., the ratio of L/Lt is about 0.5:1 to about 0.6:1).

With continued reference to FIGS. 1-3, in a configuration of the insert bit 10 having an overall length Lt of about 1 inch, a ratio of the radius R to the length L is equal to about 0.43:1 to about 3.75:1. Alternatively, in a configuration of the insert bit 10 having an overall length Lt of about 2 inches, a ratio of the radius R to the length L is equal to about 1.21:1 to about 5.5:1. Further, in a configuration of the insert bit 10 having an overall length Lt of about 3 inches, a ratio of the radius R to the length L is equal to about 4.12:1 to about 10:1. In the illustrated construction of the insert bit 10, which is configured having an overall length Lt of about 2 inches, the length L of the concave portion 30 of the shank 22 is about 0.514 inches, and the radius R of the concave portion 30 of the shank 22 is about 1.149 inches. As such, the ratio of the radius R to the length L is about 2.24:1. Also, in the illustrated construction of the insert bit 10, the diameter D1 of the mid-portion 38 is about 71% of the diameter D2 of each of the end portions 34. Alternatively, the diameter D1 of the mid-portion 38 may be about 60% to about 80% of the diameter D2 of each of the end portions 34. Further, the diameter D1 of the mid-portion 38 may be as large as about 0.236 inches. Alternatively, the diameter D1 of the mid-portion 38 may be as small as about 0.1 inches.

With reference to FIGS. 1-3 and 6, the insert bit 10 also includes an identification band 50 coupled to the shank 22. As shown in FIG. 6, the band 50 is shaped as a ring and is made from elastomeric material having a Scale A durometer of about 70 to about 90. Further, the inside diameter of the band 50 is less than the width of the Philips-style tip 18, such that the band 50 must be stretched when inserted over the tip 18 and onto the shank 22. Alternatively, the band 50 may be made from a thin, heat-shrinkable material that is inserted over the tip 18 and shrunk with application of heat onto the shank 22. Further, the band 50 may be configured with a non-cylindrical outer surface (e.g., a hexagonal outer surface).

With continued reference to FIG. 6, the shank 22 includes a circumferential groove 54 positioned between the concave portion 30 of the shank 22 and the drive portion 14 into which the band 50 is at least partially received. An inside diameter of the band 50 is less than or approximately equal to a width or thickness of the shank 22 in the groove 54 to yield an interference fit between the band 50 and the shank 22. In other words, the band 50 is at least partially stretched from its naturally occurring or unstretched shape after it is assembled onto the shank 22. In addition to the interference fit between the band 50 and the shank 22, an adhesive may be utilized to more permanently secure the band 50 to the shank 22. Alternatively, the circumferential groove 54 in the shank 22 may be omitted, and the band 50 may be positioned over a cylindrical portion of the shank 22 having an outer diameter greater than that of the concave portion 30 of the shank 22. Further, the band 50 may be coupled to the insert bit 10 in a different location along the length of the insert bit 10.

The identification band 50 may include any of a number of different indicators 58 (FIG. 1) associated with a particular characteristic of the insert bit 10. For example, the indicator 58 may be configured as a logo or design printed upon, impregnated into, or molded into the identification band 50 to indicate a manufacturer or brand of the insert bit 10. In addition, numbers, letters, or any combination thereof may be printed upon, impregnated into, or molded into the identification band 50 to indicate the particular size of the insert bit 10. Further, the color of the identification band 50 may serve as an indicator of a particular characteristic of the insert bit 10 (e.g., a manufacturer or brand identifier, sizing of the insert bit 10, etc.).

The insert bit 10 is manufactured from bar stock having a hexagonal cross-section. The tip 18 of the insert bit 10 is forged, and the concave portion 30 of the shank 22 is machined to a particular length L and a particular radius R (FIG. 2) to facilitate elastic deformation of the concave portion 30 of the shank 22 when the insert bit 10 is utilized with an impact driver. In addition, a machining process may be employed to create the circumferential groove 54 in the shank 22 in which the identification band 50 is positioned. Alternatively, any of a number of different manufacturing processes may be employed to create the insert bit 10. The insert bit 10 is also heat treated using a tempering process to a hardness range between 52-60 HRC. Alternatively, the insert bit 10 may be heat treated to a hardness range between 54-59 HRC. The same heat treating process is applied to the entire length of the insert bit 10, such that the resultant hardness of the insert bit 10 is substantially uniform or non-varying, within a tolerance value, along the entire length of the insert bit 10. In other words, the hardness of the concave portion 30 of the shank 22 is similar to that of the tip 18 and the drive portion 14 of the insert bit 10. Alternatively, a heat treating process may be employed to impart a varying hardness along the length of the insert bit 10. Particularly, the shank 22 may be heat treated such that the hardness of the shank 22 varies along the length L of the concave portion 30.

In operation of the insert bit 10, the concave portion 30 of the shank 22 is configured to increase the impact resistance or the toughness of the insert bit 10, such that the tip 18 of the insert bit 10 is allowed to elastically deform or twist relative to the drive portion 14 about the central axis 46 of the insert bit 10. Specifically, the polar moment of inertia of the shank 22 is decreased by incorporating the concave portion 30, thereby reducing the amount of torsion required to elastically twist the shank 22, compared to a configuration of the shank 22 having a cylindrical shape (i.e., without the reduced diameter mid-portion 38).

FIGS. 7-11 illustrate another construction of an insert bit 10 a similar to the insert bit 10 of FIGS. 1-6, with like components or features having like reference numerals including the letter “a.” However, the identification band 50 is omitted in the insert bit 10 a of FIGS. 7-11 (FIGS. 7-9). Rather, the concave portion 30 a of the shank 22 a extends across the entire length La of the shank 22 a. Also, the diameter D3 of the end portion 34 a adjacent the drive portion 14 a is larger than the diameter D2 of the end portion 34 a adjacent the tip 18 a. Specifically, the diameter D1 of the mid-portion 38 a is about 55% of the diameter D3 of the end portion 34 a adjacent the drive portion 14 a. Alternatively, the diameter D1 may be about 45% to about 65% of the diameter D3. The relative values between D1 and D2 for the insert bit 10 a are similar to those for the insert bit 10. As a further alternative, the diameters D2, D3 may be substantially equal. The diameter D1 of the mid-portion 38 a may be as large as about 0.236 inches. Alternatively, the diameter D1 of the mid-portion 38 a may be as small as about 0.1 inches. The method of manufacturing the insert bit 10 a and the manner of operation of the insert bit 10 a are substantially similar to that described above with respect to the insert bit 10.

FIGS. 12-16 illustrate another construction of an insert bit 10 b similar to the insert bits 10, 10 a of FIGS. 1-6 and 7-11, respectively, with like components or features having like reference numerals including the letter “b.” The identification band 50 is omitted in the insert bit 10 b of FIGS. 12-16, and the groove of the drive portion (FIGS. 1-3 and FIGS. 7-9) is omitted in the insert bit 10 b of FIGS. 12-16. Like the insert bit 10 a of FIGS. 7-11, the concave portion 30 b of the shank 22 b extends across the entire length Lb of the shank 22 b. The method of manufacturing the insert bit 10 b and the manner of operation of the insert bit 10 b are substantially similar to that described above with respect to the insert bit 10. However, the insert bit 10 b may not be utilized with a driver incorporating quick-release structure (e.g., a ball detent) because of the omission of the groove 26 in the drive portion 14 b. The insert bit 10 b may, however, be utilized with a driver employing an interference fit to secure the insert bit 10 b to the driver.

FIGS. 17 and 18 illustrate another construction of an insert bit 10 c similar to the insert bit 10 of FIGS. 1-6, with like components or features having like reference numerals with a letter “c.” The insert bit 10 c is configured with a shorter overall length Lt than that of the insert bit 10. Specifically, the length of the drive portion 14 c is less than the length of the drive portion 14 of the insert bit 10, and the length Lc of the concave portion 30 c is less than the length L of the concave portion 30 of the insert bit 10. Also, the groove 26 is omitted in the drive portion 14 c the insert bit 10 c, such that the insert bit 10 c may not be utilized with a driver incorporating a quick-release structure (e.g., a ball detent). The insert bit 10 c may, however, be utilized with a driver employing an interference fit to secure the insert bit 10 c to the driver.

Specifically, the insert bit 10 c of FIGS. 17 and 18 is configured having an overall length Lt of about 1 inch. The curvature of the concave portion 30 c is defined by a radius Rc of about 0.08 inches to about 0.75 inches, and the length Lc of the concave portion 30 c of the shank 22 c is about 0.15 inches to about 0.35 inches. Therefore, a ratio of the radius Re of the concave portion 30 c to the overall length Lt is about 0.08 to about 0.75, and a ratio of the length Lc of the concave portion 30 c of the shank 22 c to the overall length Lt is about 0.15 to about 0.35. The diameter D1 of the mid-portion 38 c may be as large as about 0.236 inches. Alternatively, the diameter D1 of the mid-portion 38 c may be as small as about 0.1 inches. The method of manufacturing the insert bit 10 c and the manner of operation of the insert bit 10 c are substantially similar to that described above with respect to the insert bit 10.

FIGS. 19-22 illustrate another construction of a tool bit or an insert bit 10 d including a hexagonal drive portion 14 d, a head or tip 18 d configured to engage a fastener, and a shank 22 d interconnecting the drive portion 14 d and the tip 18 d. The hexagonal drive portion 14 d is intended to be engaged by any of a number of different tools, adapters, or components to receive torque from the tool, adapter, or component to rotate the insert bit 10 d. For example, the insert bit 10 d may be utilized with a driver including a socket (not shown) having a corresponding hexagonal recess in which the hexagonal drive portion 14 d of the insert bit 10 d is received. The driver may also include a stem extending from the socket, which may be coupled to a handle for hand-use by an operator or to a chuck of a power tool (e.g., a drill) for powered use by the operator. An interference fit between the hexagonal drive portion 14 d of the insert bit 10 d and the socket may be used to axially secure the insert bit 10 d to the driver. Alternatively, a quick-release structure may be employed to axially secure the insert bit 10 d to the driver. With reference to FIGS. 19 and 20, the drive portion 14 d of the insert bit 10 d includes a groove 26 d into which the quick-release structure (e.g., a ball detent) may be positioned to axially secure the insert bit 10 d to the driver. Alternatively, the groove 26 d may be omitted from the drive portion 14 d of the insert bit 10 d should an interference fit between the socket and the drive portion 14 d be employed.

With continued reference to FIGS. 19 and 20, the tip 18 d of the insert bit 10 d is configured as a Philips-style tip 18 d (see also FIG. 21). Alternatively, the tip 18 d of the insert bit 10 d may be differently configured to engage different style fasteners. For example, the tip 18 d of the insert bit 10 d may be configured as a straight blade (otherwise known as a “regular head”) to engage fasteners having a corresponding straight slot.

With reference to FIG. 20, a portion 30 d of the shank 22 d is concave, including opposite end portions 34 d and a reduced diameter mid-portion 38 d. The concave portion 30 d of the shank 22 d includes an outer peripheral surface 42 d having a curvature in a plane including a central axis 46 d (FIG. 19) of the insert bit 10 d (i.e., in a plane parallel to the plane of the page of FIG. 20). In a configuration of the insert bit 10 d having an overall length Lt of about 3.5 inches, the curvature is defined by a radius Rd of about 3 inches to about 50 inches. More particularly, in a configuration of the insert bit 10 d having an overall length Lt of about 3.5 inches, the curvature is defined by a radius Rd of about 5 inches to about 5.5 inches. In other words, in a configuration of the insert bit 10 d having an overall length Lt of about 3.5 inches, a ratio of the radius Rd of the curvature of the outer peripheral surface 42 d of the shank 22 d to the length Lt of the insert bit 10 d is between about 0.50:1 and about 14.3:1. More particularly, in a configuration of the insert bit 10 d having an overall length Lt of about 3.5 inches, a ratio of the radius Rd of the curvature of the outer peripheral surface 42 d of the shank 22 d to the length Lt of the insert bit 10 d is between about 1.25:1 and about 1.75:1.

With continued reference to FIG. 20, in a configuration of the insert bit 10 d having an overall length Lt of about 3.5 inches, a ratio of the length Ld of the concave portion 30 d of the shank 22 d to the overall length Lt of the insert bit 10 d is about 0.2:1 to about 0.7:1. More particularly, in a configuration of the insert bit 10 d having an overall length Lt of about 3.5 inches, a ratio of the length Ld of the concave portion 30 d of the shank 22 d to the overall length Lt of the insert bit 10 d is about 0.3:1 to about 0.4:1. Considering the above ratios of the radius Rd to the length Lt, a ratio of the radius Rd of the curvature of the outer peripheral surface 42 d of the shank 22 d to the length Ld of the concave portion 30 d of the shank 22 d is between about 0.7:1 and about 71.5:1. More particularly, in a configuration of the insert bit 10 d having an overall length Lt of about 3.5 inches, the ratio of the radius Rd of the curvature of the outer peripheral surface 42 d of the shank 22 d to the length Ld of the concave portion 30 d of the shank 22 d is between about 3.1:1 and about 5.8:1. Also, in a configuration of the insert bit 10 d having an overall length Lt of about 3.5 inches, a ratio of the diameter D1 of the mid-portion 38 d to the diameter D2 of each of the end portions 34 d is about 0.7:1 to about 0.8:1. The diameter D1 of the mid-portion 38 d may be as large as about 0.236 inches. Alternatively, the diameter D1 of the mid-portion 38 d may be as small as about 0.1 inches.

With reference to FIGS. 19 and 20, the drive portion 14 d and the tip 18 d are coated with a layer or coating (e.g., manganese phosphate, etc.) to inhibit corrosion of the insert bit 10 d. In addition, the concave portion 30 d of the shank 22 d is at least partially polished to a surface finish of at least about 2 microns to remove the coating from the shank 22 d. Alternatively, the concave portion 30 d of the shank 22 d may be polished to a surface finish of about 1 micron to about 2 microns to remove the coating from the shank 22 d. In the illustrated construction of the insert bit 10 d, the shank 22 d is polished along the entire length of the outer peripheral surface 42 d of the shank 22 d having the curvature Rd (i.e., the concave portion 30 d). Alternatively, less of the concave portion 30 d may be polished than what is shown in FIGS. 19 and 20.

The insert bit 10 d is manufactured from bar stock having a hexagonal cross-section. The tip 18 d of the insert bit 10 d is forged, and the concave portion 30 d of the shank 22 d is machined to a particular length Ld and a particular radius Rd (FIG. 20) to facilitate elastic deformation of the concave portion 30 d of the shank 22 d when the insert bit 10 d is utilized with an impact driver. Alternatively, any of a number of different manufacturing processes may be employed to create the insert bit 10 d. The insert bit 10 d is then heat treated using a tempering process to a hardness range between about 52 HRC and about 60 HRC. Alternatively, the insert bit 10 d may be heat treated to a hardness range between about 54 HRC and about 59 HRC The same heat treating process is applied to the entire length of the insert bit 10 d, such that the resultant hardness of the insert bit 10 d is substantially uniform or non-varying, within a tolerance value, along the entire length of the insert bit 10 d. In other words, the hardness of the concave portion 30 d of the shank 22 d is similar to that of the tip 18 d and the drive portion 14 d of the insert bit 10 d. Alternatively, a heat treating process may be employed to impart a varying hardness along the length of the insert bit 10 d. Particularly, the shank 22 d may be heat treated such that the hardness of the shank 22 d varies along the length Ld of the concave portion 30 d.

After the insert bit 10 d is heat treated, the corrosion-resistant coating or layer (e.g., manganese phosphate, etc.) is applied to the entire insert bit 10 d to inhibit corrosion of the insert bit 10 d. The corrosion-resistant coating or layer may be applied in any of a number of different ways (e.g., using a spraying or dipping process, plating, painting, steam tempering, etc.). After the insert bit 10 d is coated, the concave portion 30 d of the shank 22 d is polished to a surface finish of at least about 2 microns to remove the corrosion-resistant coating or layer from the shank 22 d. In the illustrated construction of the insert bit 30 d, the concave portion 30 d is polished using an abrasive paper or sandpaper. Alternatively, the concave portion 30 d may be polished in any of a number of different manners (e.g., by electroplating, bead-blasting, using a vibration process with abrasives, etc.).

In operation of the insert bit 10 d, the concave portion 30 d of the shank 22 d is configured to increase the impact resistance or the toughness of the insert bit 10 d, such that the tip 18 d of the insert bit 10 d is allowed to elastically deform or twist relative to the drive portion 14 d about the central axis 46 d of the insert bit 10 d. Specifically, the polar moment of inertia of the shank 22 d is decreased by incorporating the concave portion 30 d, thereby reducing the amount of torsion required to elastically twist the shank 22 d, compared to a configuration of the shank 22 d having a cylindrical shape (i.e., without the reduced diameter mid-portion 38 d). By polishing the concave portion 30 d of the shank 22 d, the number and size of the microcracks in the concave portion 30 d of the shank 22 d are reduced, which otherwise might result in undesirably high stress risers in the concave portion 30 d that could ultimately shorten the useful life of the insert bit 10 d when used in an impact application.

FIGS. 23-26 illustrate another construction of a tool bit or an insert bit 10 e similar to the insert bit 10 d of FIGS. 19-22, with like components or features having like reference numerals including the letter “e.” With reference to FIGS. 23-25, the tip 18 e of the insert bit 10 e is configured as a square tip 18 d configured to be received within a fastener having a square recess.

In a configuration of the insert bit 10 e having an overall length Lt of about 3.5 inches, the curvature of the concave portion 30 e is defined by a radius Re of about 3 inches to about 50 inches (FIG. 24). More particularly, in a configuration of the insert bit 10 e having an overall length Lt of about 3.5 inches, the curvature of the concave portion 30 e is defined by a radius Re of about 5 inches to about 5.5 inches. In other words, in a configuration of the insert bit 10 e having an overall length Lt of about 3.5 inches, a ratio of the radius Re of the curvature of the outer peripheral surface 42 e of the shank 22 e to the length Lt of the insert bit 10 e is between about 0.50:1 and about 14.3:1. More particularly, in a configuration of the insert bit 10 e having an overall length Lt of about 3.5 inches, a ratio of the radius Re of the curvature of the outer peripheral surface 42 e of the shank 22 e to the length Lt of the insert bit 10 e is between about 1.25:1 and about 1.75:1.

With continued reference to FIG. 24, in a configuration of the insert bit 10 e having an overall length Lt of about 3.5 inches, a ratio of the length Le of the concave portion 30 e of the shank 22 e to the overall length Lt of the insert bit 10 e is about 0.2:1 to about 0.7:1. More particularly, in a configuration of the insert bit 10 e having an overall length Lt of about 3.5 inches, a ratio of the length Le of the concave portion 30 e of the shank 22 e to the overall length Lt of the insert bit 10 e is about 0.3:1 to about 0.4:1. Considering the above ratios of the radius Re to the length Lt, a ratio of the radius Re of the curvature of the outer peripheral surface 42 e of the shank 22 e to the length Le of the concave portion 30 e of the shank 22 e is between about 0.7:1 and about 71.5:1. More particularly, in a configuration of the insert bit 10 e having an overall length Lt of about 3.5 inches, the ratio of the radius Re of the curvature of the outer peripheral surface 42 e of the shank 22 e to the length Le of the concave portion 30 e of the shank 22 e is between about 3.1:1 and about 5.8:1. Also, in a configuration of the insert bit 10 e having an overall length Lt of about 3.5 inches, a ratio of the diameter D1 of the mid-portion 38 e to the diameter D2 of each of the end portions 34 e is about 0.7:1 to about 0.8:1. The diameter D1 of the mid-portion 38 e may be as large as about 0.236 inches. Alternatively, the diameter D1 of the mid-portion 38 e may be as small as about 0.1 inches.

Like the insert bit 10 d, the drive portion 14 e and the tip 18 e of the insert bit 10 e are coated with a layer or coating (e.g., manganese phosphate, etc.) to inhibit corrosion of the insert bit 10 e. In addition, the concave portion 30 e of the shank 22 e is at least partially polished to a surface finish of at least about 2 microns to remove the coating from the shank 22 e. Alternatively, the concave portion 30 e of the shank 22 e may be polished to a surface finish of about 1 micron to about 2 microns to remove the coating from the shank 22 e. In the illustrated construction of the insert bit 10 e, the shank 22 e is polished along the entire length of the outer peripheral surface 42 e of the shank 22 e having the curvature Re (i.e., the concave portion 30 e). The method of manufacturing the insert bit 10 e and the manner of operation of the insert bit 10 e are substantially similar to that described above with respect to the insert bit 10 d.

FIGS. 27-30 illustrate another construction of a tool bit or an insert bit 10 f similar to the insert bit 10 d of FIGS. 19-22, with like components or features having like reference numerals including the letter “f.” With reference to FIGS. 27-29, the tip 18 e of the insert bit 10 e is configured as a Philips-style tip 18 f. Alternatively, the tip 18 f may be differently configured to engage different style fasteners. For example, the tip 18 f may be configured as a straight blade (otherwise known as a “regular head”) to engage fasteners having a corresponding straight slot.

In a configuration of the insert bit 10 f having an overall length Lt of about 2 inches, the curvature of the concave portion 30 f is defined by a radius Rf of about 1 inch to about 2 inches (FIG. 28). More particularly, in a configuration of the insert bit 10 f having an overall length Lt of about 2 inches, the curvature of the concave portion 30 f is defined by a radius Rf of about 1.5 inches. In other words, in a configuration of the insert bit 10 f having an overall length Lt of about 2 inches, a ratio of the radius Rf of the curvature of the outer peripheral surface 42 f of the shank 22 f to the length Lt of the insert bit 10 f is between about 0.50:1 and about 2:1. More particularly, in a configuration of the insert bit 10 f having an overall length Lt of about 2 inches, a ratio of the radius Rf of the curvature of the outer peripheral surface 42 f of the shank 22 f to the length Lt of the insert bit 10 f is between about 0.5:1 and about 1:1.

With continued reference to FIG. 28, in a configuration of the insert bit 10 f having an overall length Lt of about 2 inches, a ratio of the length Lf of the concave portion 30 f of the shank 22 f to the overall length Lt of the insert bit 10 f is about 0.2:1 to about 0.6:1. More particularly, in a configuration of the insert bit 10 f having an overall length Lt of about 2 inches, a ratio of the length Lf of the concave portion 30 f of the shank 22 f to the overall length Lt of the insert bit 10 f is about 0.2 inches to about 0.3 inches. Considering the above ratios of the radius Rf to the length Lt, a ratio of the radius Rf of the curvature of the outer peripheral surface 42 f of the shank 22 f to the length Lf of the concave portion 30 f of the shank 22 f is between about 0.8:1 and about 10:1. More particularly, in a configuration of the insert bit 10 f having an overall length Lt of about 2 inches, the ratio of the radius Rf of the curvature of the outer peripheral surface 42 f of the shank 22 f to the length Lf of the concave portion 30 f of the shank 22 f is between about 1.7:1 and about 5:1.

With continued reference to FIG. 28, in a configuration of the insert bit 10 f having an overall length Lt of about 2 inches, a ratio of the diameter D1 of the mid-portion 38 f to the diameters D2, D3 of the end portions 34 f is about 0.7:1 to about 0.9:1. Similar to the insert bit 10 a, the diameter D3 of the end portion 34 f adjacent the drive portion 14 f is larger than the diameter D2 of the end portion 34 f adjacent the tip 18 f. A ratio of the diameter D1 of the mid-portion 38 f to the diameter D3 of the end portion 34 f adjacent the drive portion 14 f is about 0.75:1, while a ratio of the diameter D1 of the mid-portion 38 f to the diameter D2 of the end portion 34 f adjacent the tip 18 f is about 0.83:1. Alternatively, the diameters D2, D3 may be substantially equal. The diameter D1 of the mid-portion 38 f may be as large as about 0.236 inches. Alternatively, the diameter D1 of the mid-portion 38 f may be as small as about 0.1 inches.

Like the insert bit 10 d, the drive portion 14 f and the tip 18 f of the insert bit 10 f are coated with a layer or coating (e.g., manganese phosphate, etc.) to inhibit corrosion of the insert bit 10 f. In addition, the concave portion 30 f of the shank 22 f is at least partially polished to a surface finish of at least about 2 microns to remove the coating from the shank 22 f. Alternatively, the concave portion 30 f of the shank 22 f may be polished to a surface finish of about 1 micron to about 2 microns to remove the coating from the shank 22 f. In the illustrated construction of the insert bit 10 f, the shank 22 f is polished along the entire length of the outer peripheral surface 42 f of the shank 22 f having the curvature Rf (i.e., the concave portion 30 f). The method of manufacturing the insert bit 10 f and the manner of operation of the insert bit 10 f are substantially similar to that described above with respect to the insert bit 10 d.

FIGS. 31-34 illustrate another construction of a tool bit or an insert bit 10 g similar to the insert bit 10 f of FIGS. 27-30, with like components or features having like reference numerals including the letter “g.” With reference to FIGS. 31-33, the tip 18 g of the insert bit 10 g is configured as a square tip 18 g configured to be received within a fastener having a square recess.

In a configuration of the insert bit 10 g having an overall length Lt of about 2 inches, the curvature of the concave portion 30 g is defined by a radius Rg of about 1 inch to about 2 inches (FIG. 32). More particularly, in a configuration of the insert bit 10 g having an overall length Lt of about 2 inches, the curvature of the concave portion 30 g is defined by a radius Rg of about 1.5 inches. In other words, in a configuration of the insert bit 10 g having an overall length Lt of about 2 inches, a ratio of the radius Rg of the curvature of the outer peripheral surface 42 g of the shank 22 g to the length Lt of the insert bit 10 g is between about 0.50:1 and about 2:1. More particularly, in a configuration of the insert bit 10 g having an overall length Lt of about 2 inches, a ratio of the radius Rg of the curvature of the outer peripheral surface 42 g of the shank 22 g to the length Lg of the insert bit 10 g is between about 0.5:1 and about 1:1.

With continued reference to FIG. 32, in a configuration of the insert bit 10 g having an overall length Lt of about 2 inches, a ratio of the length Lg of the concave portion 30 g of the shank 22 g to the overall length Lt of the insert bit 10 g is about 0.2:1 to about 0.6:1. More particularly, in a configuration of the insert bit 10 g having an overall length Lt of about 2 inches, a ratio of the length Lg of the concave portion 30 g of the shank 22 g to the overall length Lt of the insert bit 10 g is about 0.2:1 to about 0.3:1. Considering the above ratios of the radius Rg to the length Lt, a ratio of the radius Rg of the curvature of the outer peripheral surface 42 g of the shank 22 g to the length Lg of the concave portion 30 g of the shank 22 g is between about 0.8:1 and about 10:1. More particularly, in a configuration of the insert bit 10 g having an overall length Lt of about 2 inches, the ratio of the radius Rg of the curvature of the outer peripheral surface 42 g of the shank 22 g to the length Lg of the concave portion 30 g of the shank 22 g is between about 1.7:1 and about 5:1.

With continued reference to FIG. 32, in a configuration of the insert bit 10 g having an overall length Lt of about 2 inches, a ratio of the diameter D1 of the mid-portion 38 g to the diameters D2, D3 of the end portions 34 g is about 0.7:1 to about 0.9:1. Similar to the insert bit 10 f, the diameter D3 of the end portion 34 g adjacent the drive portion 14 g is larger than the diameter D2 of the end portion 34 g adjacent the tip 18 g. Specifically, a ratio of the diameter D1 of the mid-portion 38 g to the diameter D3 of the end portion 34 g adjacent the drive portion 14 g is about 0.74:1, while a ratio of the diameter D1 of the mid-portion 38 g to the diameter D2 of the end portion 34 g adjacent the tip 18 g is about 0.85:1. Alternatively, the diameters D2, D3 may be substantially equal. The diameter D1 of the mid-portion 38 g may be as large as about 0.236 inches. Alternatively, the diameter D1 of the mid-portion 38 g may be as small as about 0.1 inches.

Like the insert bit 10 f, the drive portion 14 g and the tip 18 g of the insert bit 10 g are coated with a layer or coating (e.g., manganese phosphate, etc.) to inhibit corrosion of the insert bit 10 g. In addition, the concave portion 30 g of the shank 22 g is at least partially polished to a surface finish of at least about 2 microns to remove the coating from the shank 22 g. Alternatively, the concave portion 30 g of the shank 22 g may be polished to a surface finish of about 1 micron to about 2 microns to remove the coating from the shank 22 g. In the illustrated construction of the insert bit 10 g, the shank 22 g is polished along the entire length of the outer peripheral surface 42 g of the shank 22 g having the curvature Rg (i.e., the concave portion 30 g). The method of manufacturing the insert bit 10 g and the manner of operation of the insert bit 10 g are substantially similar to that described above with respect to the insert bit 10 d.

FIGS. 35-38 illustrate another construction of a tool bit or an insert bit 10 h similar to the insert bit 10 f of FIGS. 27-30, with like components or features having like reference numerals including the letter “h.” With reference to FIGS. 35-37, the tip 18 h of the insert bit 10 h is configured as a TORX screw tip 18 g.

In a configuration of the insert bit 10 h having an overall length Lt of about 2 inches, the curvature of the concave portion 30 h is defined by a radius Rh of about 1 inch to about 2 inches (FIG. 36). More particularly, in a configuration of the insert bit 10 h having an overall length Lt of about 2 inches, the curvature of the concave portion 30 h is defined by a radius Rh of about 1.5 inches. In other words, in a configuration of the insert bit 10 h having an overall length Lt of about 2 inches, a ratio of the radius Rh of the curvature of the outer peripheral surface 42 h of the shank 22 h to the length Lt of the insert bit 10 h is between about 0.50:1 and about 2:1. More particularly, in a configuration of the insert bit 10 h having an overall length Lt of about 2 inches, a ratio of the radius Rh of the curvature of the outer peripheral surface 42 h of the shank 22 h to the length Lh of the insert bit 10 h is between about 0.5:1 and about 1:1.

With continued reference to FIG. 36, in a configuration of the insert bit 10 h having an overall length Lt of about 2 inches, a ratio of the length Lh of the concave portion 30 h of the shank 22 h to the overall length Lt of the insert bit 10 h is about 0.2:1 to about 0.6:1. More particularly, in a configuration of the insert bit 10 h having an overall length Lt of about 2 inches, a ratio of the length Lh of the concave portion 30 h of the shank 22 h to the overall length Lt of the insert bit 10 h is about 0.2:1 to about 0.3:1. Considering the above ratios of the radius Rh to the length Lt, a ratio of the radius Rh of the curvature of the outer peripheral surface 42 h of the shank 22 h to the length Lh of the concave portion 30 h of the shank 22 h is between about 0.8:1 and about 10:1. More particularly, in a configuration of the insert bit 10 h having an overall length Lt of about 2 inches, the ratio of the radius Rh of the curvature of the outer peripheral surface 42 h of the shank 22 h to the length Lh of the concave portion 30 h of the shank 22 h is between about 1.7:1 and about 5:1.

With continued reference to FIG. 36, in a configuration of the insert bit 10 h having an overall length Lt of about 2 inches, a ratio of the diameter D1 of the mid-portion 38 h to the diameters D2, D3 of the end portions 34 h is about 0.7:1 to about 0.95:1. Similar to the insert bit 10 f, the diameter D3 of the end portion 34 h adjacent the drive portion 14 h is larger than the diameter D2 of the end portion 34 h adjacent the tip 18 h. Specifically, a ratio of the diameter D1 of the mid-portion 38 h to the diameter D3 of the end portion 34 h adjacent the drive portion 14 h is about 0.74:1, while a ratio of the diameter D1 of the mid-portion 38 h to the diameter D2 of the end portion 34 h adjacent the tip 18 h is about 0.95:1. Alternatively, the diameters D2, D3 may be substantially equal. The diameter D1 of the mid-portion 38 h may be as large as about 0.236 inches. Alternatively, the diameter D1 of the mid-portion 38 h may be as small as about 0.1 inches.

Like the insert bit 10 f, the drive portion 14 h and the tip 18 h of the insert bit 10 h are coated with a layer or coating (e.g., manganese phosphate, etc.) to inhibit corrosion of the insert bit 10 h. In addition, the concave portion 30 h of the shank 22 h is at least partially polished to a surface finish of at least about 2 microns to remove the coating from the shank 22 h. Alternatively, the concave portion 30 h of the shank 22 h may be polished to a surface finish of about 1 micron to about 2 microns to remove the coating from the shank 22 h. In the illustrated construction of the insert bit 10 h, the shank 22 h is polished along the entire length of the outer peripheral surface 42 h of the shank 22 h having the curvature Rh (i.e., the concave portion 30 h). The method of manufacturing the insert bit 10 h and the manner of operation of the insert bit 10 h are substantially similar to that described above with respect to the insert bit 10 d.

FIGS. 39-42 illustrate another construction of a tool bit or an insert bit 10 i including a hexagonal drive portion 14 i, a head or tip 18 i configured to engage a fastener, and a shank 22 i interconnecting the drive portion 14 i and the tip 18 i. The insert bit 10 i may be utilized with a driver including a socket (not shown) having a corresponding hexagonal recess in which the hexagonal drive portion 14 i of the insert bit 10 i is received. The driver may also include a stem extending from the socket, which may be coupled to a handle for hand-use by an operator, or to a chuck of a power tool (e.g., a drill) for powered use by the operator. An interference fit between the hexagonal drive portion 14 i of the insert bit 10 i and the socket may be used to axially secure the insert bit 10 i to the driver.

With reference to FIGS. 39-41, the tip 18 i is configured as a Philips-style tip 18 i. Alternatively, the tip 18 i may be differently configured to engage different style fasteners. For example, the tip 18 i may be configured as a straight blade (otherwise known as a “regular head”) to engage fasteners having a corresponding straight slot.

With reference to FIGS. 39 and 40, the drive portion 14 i and the tip 18 i are coated with a layer or coating (e.g., manganese phosphate, etc.) to inhibit corrosion of the insert bit 10 i. In addition, at least a portion of the shank 22 i is polished to a surface finish of at least about 2 microns to remove the coating from the shank 22 i. Alternatively, the shank 22 i may be polished to a surface finish of about 1 micron to about 2 microns to remove the coating from the shank 22 i.

The insert bit 10 i is manufactured from bar stock having a hexagonal cross-section. The tip 18 i of the insert bit 10 i is forged, and the shank 22 i is machined to a substantially cylindrical shape to facilitate elastic deformation of the shank 22 i when the insert bit 10 i is utilized with an impact driver. Alternatively, any of a number of different manufacturing processes may be employed to create the insert bit 10 i. The insert bit 10 i is then heat treated using a tempering process to a hardness range between about 52 HRC and about 60 HRC. Alternatively, the insert bit 10 i may be heat treated to a hardness range between about 54 HRC and about 59 HRC. The same heat treating process is applied to the entire length of the insert bit 10 i, such that the resultant hardness of the insert bit 10 i is substantially uniform or non-varying, within a tolerance value, along the entire length of the insert bit 10 i. Alternatively, a heat treating process may be employed to impart a varying hardness along the length of the insert bit 10 i.

After the insert bit 10 i is heat treated, the corrosion-resistant coating or layer (e.g., manganese phosphate, etc.) is applied to the entire insert bit 10 i to inhibit corrosion of the insert bit 10 i. The corrosion-resistant coating or layer may be applied in any of a number of different ways (e.g., using a spraying or dipping process, plating, painting, steam tempering, etc.). After the insert bit 10 i is coated, a portion of the shank 22 i is polished to a surface finish of at least about 2 microns to remove the corrosion-resistant coating or layer from the shank 22 i. In the illustrated construction of the insert bit 10 i, the shank 22 i is polished using an abrasive paper or sandpaper. Alternatively, the shank 22 i may be polished in any of a number of different manners (e.g., by electroplating, bead-blasting, using a vibration process with abrasives, etc.).

In operation of the insert bit 10 i, the shank 22 i is configured to increase the impact resistance or the toughness of the insert bit 10 i, such that the tip 18 i of the insert bit 10 i is allowed to elastically deform or twist relative to the drive portion 14 i about the central axis 46 i of the insert bit 10 i. Specifically, the polar moment of inertia of the shank 22 i is less than that of the drive portion 14 i, thereby reducing the amount of torsion required to elastically twist the shank 22 i. By polishing the shank 22 i, the number and size of the microcracks in the shank 22 i are reduced, which otherwise might result in undesirably high stress risers in the shank 22 i that could ultimately shorten the useful life of the insert bit 10 i when used in an impact application.

FIGS. 43-46 illustrate another construction of a tool bit or an insert bit 10 j, with like components or features having like reference numerals including the letter “j.” With reference to FIGS. 43-45, the tip 18 j of the insert bit 10 j is configured as a square tip 18 j configured to be received within a fastener having a square recess.

With reference to FIG. 44, the shank 22 j includes a tapered cylindrical shape defining an included angle A of about 4.5 degrees. Alternatively, the shank 22 j may include a tapered cylindrical shape defining an angle A more or less than about 4.5 degrees. As a further alternative, the shank 22 j may include a substantially cylindrical shape similar to the shank 22 i of the insert bit 10 i.

Also, like the insert bit 10 i, the drive portion 14 j and the tip 18 j of the insert bit 10 j are coated with a layer or coating (e.g., manganese phosphate, etc.) to inhibit corrosion of the insert bit 10 j. In addition, at least a portion of the shank 22 j is polished to a surface finish of at least about 2 microns to remove the coating from the shank 22 j. Alternatively, the shank 22 j may be polished to a surface finish of about 1 micron to about 2 microns to remove the coating from the shank 22 j. The method of manufacturing the insert bit 10 j and the manner of operation of the insert bit 10 j are substantially similar to that described above with respect to the insert bit 10 i.

FIGS. 47-50 illustrate another construction of a tool bit or an insert bit 10 k that is similar to the insert bit 10 j of FIGS. 43-46, with like components or features having like reference numerals including the letter “k.” With reference to FIGS. 47-49, the tip 18 k of the insert bit 10 k is configured as a TORX screw tip 18 k.

With reference to FIG. 48, the shank 2 kj includes a tapered cylindrical shape defining an included angle A of about 4.5 degrees. Alternatively, the shank 22 k may include a tapered cylindrical shape defining an angle A more or less than about 4.5 degrees. As a further alternative, the shank 22 k may include a substantially cylindrical shape similar to the shank 22 i of the insert bit 10 i.

Also, like the insert bits 10 i, 10 j, the drive portion 14 k and the tip 18 k of the insert bit 10 k are coated with a layer or coating (e.g., manganese phosphate, etc.) to inhibit corrosion of the insert bit 10 k. In addition, at least a portion of the shank 22 k is polished to a surface finish of at least about 2 microns to remove the coating from the shank 22 k. Alternatively, the shank 22 k may be polished to a surface finish of about 1 micron to about 2 microns to remove the coating from the shank 22 k. The method of manufacturing the insert bit 10 k and the manner of operation of the insert bit 10 k are substantially similar to that described above with respect to the insert bit 10 i.

Various features of the invention are set forth in the following claims. 

What is claimed is:
 1. A method of manufacturing a tool bit, the method comprising: machining a working end into a piece of hexagonal bar stock; machining a shank adjacent the working end, leaving a hexagonal drive portion adjacent the shank; heat treating the tool bit; applying a coating to the working end, the shank, and the hexagonal drive portion of the tool bit to inhibit corrosion of the tool bit; and polishing at least a portion of the shank to remove the coating from the portion of the shank.
 2. The method of claim 1, wherein machining the shank includes machining a curvature into an outer peripheral surface of the shank, the curvature defined in a plane including a central axis of the tool bit.
 3. The method of claim 2, wherein machining the curvature into the outer peripheral surface of the shank includes sizing the machined length of the shank in which a ratio of the length of the outer peripheral surface having the curvature to the length of the tool bit is between about 0.2:1 and about 0.7:1.
 4. The method of claim 2, wherein machining the curvature into the outer peripheral surface of the shank includes sizing the machined length of the shank in which a ratio of the length of the outer peripheral surface having the curvature to the length of the tool bit is between about 0.3:1 and about 0.4:1.
 5. The method of claim 2, wherein machining the curvature into the outer peripheral surface of the shank includes sizing the machined length of the shank in which a ratio of the length of the outer peripheral surface having the curvature to the length of the tool bit is between about 0.2:1 and about 0.3:1.
 6. The method of claim 2, wherein machining the curvature into the outer peripheral surface of the shank includes sizing the curvature in which a ratio of the radius of the curvature of the outer peripheral surface of the shank to the length of the tool bit is between about 0.50:1 and about 14.3:1.
 7. The method of claim 2, wherein machining the curvature into the outer peripheral surface of the shank includes sizing the curvature in which a ratio of a radius of the curvature of the outer peripheral surface of the shank to the length of the tool bit is between about 1.25:1 and about 1.75:1.
 8. The method of claim 2, wherein machining the curvature into the outer peripheral surface of the shank includes sizing the curvature in which a ratio of the radius of the curvature of the outer peripheral surface of the shank to the length of the outer peripheral surface having the curvature is between about 0.5:1 and about 1:1.
 9. The method of claim 2, wherein machining the curvature into the outer peripheral surface of the shank includes sizing the curvature to define a maximum diameter of the shank and a minimum diameter of the shank, and wherein a ratio of the minimum diameter to the maximum diameter is between about 0.7:1 and about 0.95:1.
 10. The method of claim 2, wherein the curvature is machined to define a radius between about 3 inches and about 50 inches.
 11. The method of claim 2, wherein the curvature is machined to define a radius between about 1 inch and about 2 inches.
 12. The method of claim 1, wherein heat treating the tool bit further includes heat treating the tool bit to a hardness between about 52 HRC and about 60 HRC.
 13. The method of claim 1, wherein polishing the shank further includes polishing the shank to a surface finish of at least about 2 microns.
 14. The method of claim 2, wherein polishing the shank further includes polishing the shank along the entire length of the outer peripheral surface having the curvature.
 15. The method of claim 1, further comprising leaving the hexagonal drive portion and the working end unpolished. 